Ultech Corporation DV2000 User Manual page 36

36 ULTECH DV2000 User's Manual
Image Data Section of a UYC File
The image data section contains all of the Y, C, and alpha data (see Converting RGB to
YCRCB that follows). The origin of the DV2000 coordinate system is the upper left (line 0 is
at the top and pixel 0 is at the left edge). The image data is arranged into lines to facilitate
faster transfer to the DV2000. Each line of image data consists of a line of Y data, a line of
C data, and a line of alpha data. The order of the lines of data is dependent on the type of
compression.
For uncompressed UYC files (compression = 0) the line of Y data is written first, then the
line of C data, then the line of alpha data. The following pseudo code illustrates how to write
an uncompressed UYC file.
write the file header
for L = 0 to (Y size - 1)
next L
For compressed UYC files (compression != 0) the line of alpha data is written first, then the
line of Y data, then the line of C data. Also each line of alpha, Y, and C data is compressed
to reduce file size (see Appendix B - UYC RLE Compression). For simplicity, the compres-
sion is only applied to one line of data at a time so that the decompression algorithm doesn't
have to find the boundaries between each line of compressed data. The following pseudo
code illustrates how to write a compressed UYC file.
write the file header
for L = 0 to (Y size - 1)
next L
for P = 0 to ((X size/2) - 1)
write the Y data for line L and pixel pair P
next P
for P = 0 to ((X size/2) - 1)
write the C data for line L and pixel pair P
next P
for P = 0 to ((X size/2) - 1)
write the alpha data for line L and pixel pair P
next P
compress the line of alpha data for line L
write the compressed line of alpha data
compress the line of Y data for line L
write the compressed line of Y data
compress the line of C data for line L
write the compressed line of C data